1. Field of Invention
This invention relates to an aerodynamic means that mitigate wind generated vortices and uplift loads on the roof perimeter area of a building, in a simple, effective, and economical way, applicable for both new constructions and retrofits of existing buildings.
2. Discussion of Prior Art
Current roof construction practices normally result in a roof perimeter configuration that tends to generate strong edge vortex and subjects the roof perimeter area to severe uplift and high risk of wind damage. Structural methods have been traditionally used to counter the severe uplift force and mitigate the risk of wind damage, while few aerodynamic methods have been recommended to reduce the uplift force. Banks et. al. described in U.S. Pat. No. 6,601,348 (2003) various types of wind spoilers supported above the roof plane to mitigate roof edge vortex. However, the apparatus is rather complicated in shape and structure, and is susceptible to wind damage itself because the raised structure subjects itself to accelerated airflow across the roof edge. In U.S. Pat. No. 4,005,557 (1977), Kramer et. al. described designs for a roof wind spoiler system claimed to be used near roof comers. The limited breadth of the apparatus impedes its effectiveness and causes higher wind loads on the adjacent segments of a roof perimeter where the apparatus does not extend. Ponder disclosed in U.S. Pat. No. 5,918,423 (1999) a wind spoiler ridge cap that is designed for roof ridges. The roof edge structure disclosed herein utilizes edge serration and face perforation to disrupt vortex formation, and is continuous along a roof perimeter or at least substantially extends from the roof comers towards the middle part of a roof edge. While the examples illustrated in this application are primarily for flat roofs, the conception and spirit herein demonstrated is suitable for both sloped and flat roofs. U.S. Pat. No. 5,414,965 (1995) of Kelley et. al. includes a drain-through gravel stop with limited face perforation for rainwater drainage, but the porosity is far from sufficient for airflow, and it does not provide edge serration, to effectively suppress roof edge vortex.
In U.S. Pat. No. 6,606,828 (2003) of this applicant et al., a series of roof edge configurations are recommended for use to mitigate vortex and high uplift in flat-roof perimeter areas, where the concept is one of coordinated exterior curvature design for a roof edge system. The present invention discloses a distinct roof edge apparatus that utilizes roof perimeter plates having face perforation and/or edge serration, which disrupt and mitigate roof edge vortices and thus reduce uplift force and wind scouring on a roof.